method and apparatus to prevent deflagration in dryers

ABSTRACT

An apparatus and method for detecting a fire in a household dryer and responding thereto.

BACKGROUND OF THE INVENTION

Dryers are well-known appliances for drying clothing and other fabric items, such as towels, sheets, blankets, and the like. Household dryers include a cabinet enclosing a horizontally rotating drum sized to receive a load of fabric items and accessible through an access door at the front of the cabinet. A motor drives rotation of the drum. The motor may also drive a blower or fan which delivers dry, heated or unheated air to the drum for drying the clothing items. A heater is typically positioned in an air inlet assembly upstream of the drum for heating the air as it flows through the dryer. The blower exhausts humid air from the drum through an exhaust outlet assembly to a discharge location exterior of the cabinet.

Recently, it has been a trend to reduce energy consumption and to make household dryers more “green”, which has led to the elimination of air gaps between the drum and the front and rear walls to better seal the drum and eliminate heat loss to the atmosphere. When the blower is off, the better sealing of the drum provides such little flow of air into the drum that if there were ever a fire in the drum the fire could be a smoldering fire because there is insufficient air for full combustion. Smoldering fires tend to generate greater amounts of carbon monoxide than a flaming fire. The carbon monoxide may combust in response to an inrush of air, such as when the door is opened. In addition, the carbon monoxide may increase the pressure within the airtight dryer, which, if great enough, may deleteriously stress the door, increasing the likelihood of an inrush of air and a flaming combustion.

SUMMARY OF THE INVENTION

The invention relates to an apparatus and method for detecting a fire in a household dryer and initiating a deflagration prevention cycle for the dryer. The presence of a fire may be detected by determining if the level of carbon monoxide present in the dryer is indicative of a fire.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a front perspective view of a dryer according to one embodiment of the invention.

FIG. 2 is a schematic view of a dryer according to one embodiment of the invention.

FIG. 3 is a schematic view of a fire detector according to a second embodiment of the invention.

FIG. 4 a is a schematic view of a second exemplary fire detector according to one embodiment of the invention.

FIG. 4 b is a schematic view of the second exemplary fire detector when smoke is present according to one embodiment of the invention.

FIG. 5 is a graph of signal strength as a function of time illustrating a typical output of a photocell that represents a fire in the dryer.

FIG. 6 is a flow chart of an exemplary method for determining if a fire is present in the dryer of FIGS. 1-2 according to one embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIG. 1 an embodiment of the invention is illustrated comprising a household dryer 10 according to one embodiment of the invention for drying clothing and other fabric items, such as towels, sheets, and blankets, having a cabinet 12 having an open face, a controller 38 having a user interface 14 for controlling operation of the dryer 10, a door 16 hingedly mounted to a front wall 20 of the cabinet 12, a rear wall 24, and a pair of side walls 22 supporting a top wall 26.

A drum 34 disposed between opposing rear and front panels 34A and 34B forms a drying chamber 18. The drum 34 may be a rotatable cylinder having rear and front edges that are received within sealed channels of the rear and front panels 34A, 34B. The front panel 34B may have an opening that aligns with the open face of the front wall 20, although other configurations known to those skilled in the art are also possible. The rotatable drum 34 may be driven in a traditional manner by a motor (not shown).

The drum 34 may have a circumference larger than that of the door 16 such that part of the front wall 20 covers a portion of the front face of the drum 34. Thus, when the door 16 is in a closed position it closes the face of the housing 12 but not the entire face of the drum 34. However, the drum 34 may be considered to be closed when the door 16 is in the closed position because the door 16 does effectively close the front face of the drum 34. The relative size of the circumference of the door to that of the drum, however, is not germane to the invention.

Referring to FIG. 2, the dryer 10 may also have a heater 36 and an air circulation system that typically includes a fan 37 for forcing air heated by the heater 36 through the drying chamber 18 to dry the fabric items held therein. The fan is typically a blower driven by the motor (not shown) that rotates the drum 34, although, the fan may have its own motor in other embodiments of the invention. The heater 36 may be operably coupled to the controller 38 such that the controller 38 may selectively energize the heater 36 to heat the air circulated through the drying chamber 18.

Additionally, the door 16 may include a lock, such as a solenoid-activated lock 40 that may be selectively locked by the controller 38. Other types of locks known to those skilled in the art may also be used. The lock 40 may be operably coupled to the controller 38 such that the controller 38 may selectively actuate the lock 40.

A fire detector 50 may be provided for detecting a fire in the dryer 10. The fire detector is illustrated as being located inside the cabinet 12, exteriorly of the drum 34, but it may be located elsewhere, including within the drum or external to the cabinet. The fire detector 50 may be configured to provide a signal to the controller 38 that is indicative of a fire or a potential for a fire, e.g., smoke or smoldering exists, or a signal to the controller 38 that the controller 38 can then use to determine if a fire or potential for a fire is indicated.

The fire detector 50 may be any suitable single or combination of devices or sensors used to detect the presence of a fire or the potential for a fire. Several parameters may indicate the presence or potential of a fire; these include temperature, smoke, and carbon monoxide, as well as other parameters, individually or combined, known to those skilled in the art. As such, for example, a temperature sensor, a smoke detector and a carbon monoxide detector may be used to detect the presence or potential of a fire. When there is incomplete combustion inside the dryer 10 large amounts of smoke will typically be present in the cabinet 12. Such combustion will also typically produce heat. Further, carbon monoxide may be produced in large amounts in a smoldering fire because there is often incomplete combustion inside the dryer 10.

While smoke and carbon monoxide may be used as indicators of fire or potential of fire, it should be noted that smoke is not necessarily detected by a carbon monoxide fire detector and carbon monoxide is not necessarily detected by a smoke detector. A suitable carbon monoxide detector may sense the level of carbon monoxide in the cabinet 12, or more specifically in the drum 34, and output an electrical signal to the controller 38 to indicate the presence or likelihood of a fire. The level of carbon monoxide that indicates that a fire may be present may be empirically determined for each type of carbon monoxide fire detector. Alternatively, a fire or a potential for a fire may be analytically determined. In that case, when a trigger value level of carbon monoxide is detected by a sensor a fire is present.

Regardless of the type of fire detector 50, when a fire or fire potential is indicated from the output of the fire detector 50, the controller 38 may be programmed to take action to minimize the deleterious effect of the fire. The controller 38 may lock the door, shut off the heater 36, turn off the fan, spray water into the drum 34 (in the case of some models of dryers, for example), etc. These actions may be taken alone, in various combinations, or as part of a specific operating cycle implement by the controller 38.

In the case of a smoldering fire where carbon monoxide may lead to a deflagration attributable to the inrush of air upon the opening of the door, the controller 38 may initiate a deflagration prevention cycle for the dryer 10 that operates the solenoid-activated lock 40 and locks the door 16 to the dryer 10. The deflagration prevention cycle may also shut off the power to the heater 36, shut off the fan, and may shut off the power to the entire dryer 10. It should be noted that the deflagration prevention cycle reduces the likelihood of a deflagration and may not absolutely prevent a deflagration. In this sense, the term prevention is used to mean both an absolute prevention as well as a reduction in the likelihood of the deflagration occurring.

FIG. 3 illustrates one specific example of a suitable fire detector 50. The fire detector 50 may be in the form of a photoelectric detector that includes a light source 53 and a photocell 55. This photoelectric detector may detect the level of smoke in the cabinet 12 and thus detect if a fire or potential for a fire may be present. A photoelectric detector may be one of several types known to those skilled in the art. As illustrated in FIG. 3, the photocell 55 measures the transmitted light from the light source 53. The photocell 55 outputs a varying electrical signal to the controller 38 depending on the amount of light it receives from the light source 53. Smoke may block the transmitted light on its way to the photocell 55. In this case, the reduction in light reaching the photocell 55 causes a significant change in the signal being sent to the controller 38 and in response the controller 38 may determine that a fire is likely or present in the dryer 10 and initiate a deflagration prevention cycle for the dryer 10.

Another exemplary photoelectric detector that uses light intensity from back scattering to detect a fire or the potential thereof is illustrated in FIGS. 4 a-4 b. In essence, light may be scattered by smoke particles onto a photocell, initiating a deflagration prevention cycle for the dryer. This type of fire detector 100 may include a T-shaped chamber 110 (although other shapes are also possible) with a light source 153 that shoots a beam of light across the horizontal bar of the T-shaped chamber 110. A photocell 155, positioned at the bottom of the vertical base of the T-shaped chamber 110, generates a current when exposed to light. Under smoke-free conditions, such as those shown in FIG. 4 a, the light beam crosses the top of the T-shaped chamber 110 in an uninterrupted straight line, not striking the photocell 155 positioned at a right angle below the beam. When smoke occurs, such as shown in FIG. 4 b, the smoke particles scatter the light, and some of the light may be directed down the vertical part of the T-shaped chamber 110 to strike the photocell 155. When sufficient light hits the photocell 155, the current triggers the controller 38 to initiate the deflagration prevention cycle.

For the described photoelectric detector, the controller 38 may have a memory in which it stores a range of values representative of a normal output of a photocell 55 when light transmits normally and no fire exists. The controller 38 may compare the stored values representative of the normal output range and the actual output received from the photocell 55 to detect the presence of a fire in the dryer 10. The controller 38 may determine if the actual output received is less than the stored values representative of the normal output range of the photocell 55 to determine the presence or likelihood of a fire. The predetermined range of values representative of a normal output of a photocell 55 and thus the threshold values to determine if a fire exists may be empirically or otherwise determined. A normal output of a photocell 55 may be determined empirically for each type of photocell to be used.

FIG. 5 is a representation of the data output of a photocell 55 as a function of time. The large decline at point A illustrates a typical output of a photocell 55 when smoke blocks the transmitted light from the light source 53. At this point, a fire may have started and the sensor may output a signal indicative of a fire or smoke or the controller may be receiving the signal and determine that a fire or smoke is indicated. A large shift from the normally expected output of the photocell 55, or a drop below some empirically determined threshold, indicates a fire exists.

In operation, a user fills the drum 34 with a fabric load, selects a cycle, and enters user inputs, such as the desired dryness level and the load size, through the control panel 14. When the drying cycle begins, the controller 38 activates the heater 36 to begin a heating cycle. The photocell 55 detects the light emitted from the light source 53 and communicates the signal strength to the controller 38. If the signal strength is above the determined threshold, then the controller 38 continues to evaluate the signal strength output from the photocell 55 for so long as the dryer 10 remains in operation. If the signal strength may be determined to be below the allowable threshold then the controller 38 invokes a suitable deflagration prevention cycle. In one embodiment of the invention, normal use of the dryer may be intentionally disabled by the controller 38 after the deflagration prevention cycle initiates and service will have to be provided before the dryer 10 may become operational again.

FIG. 6 provides a flow chart corresponding to an exemplary method for preventing deflagration 200 of the dryer 10 according to an embodiment of the invention. The method for preventing deflagration 200 may be implemented in any suitable manner, such as an automatic cycle of the dryer 10 that continuously runs as long as the dryer 10 remains in operation. The method for preventing deflagration 200 begins with a first determination at a step 202 of whether a fire or the potential for a fire exists based on the fire detector. If a fire exists then the door 16 may be locked at a step 204. After the door 16 locks in step 204 additional steps may follow such as terminating the operation of the heater in step 206, which may be done by shutting off or terminating power to the heater 36, terminating operation of the fan in step 208, which may be done by shutting off or terminating the fan, and terminating operation of the entire dryer, which may be done by shutting off or terminating power to the entire dryer in step 210.

Other steps may also be taken as part of the deflagration prevention cycle 100. For example, an alarm may be sounded to alert the user or anyone near by. If the appliance has a data or voice communication functionality, a suitable alarm may be sent to a remote location, which may include the consumer, a security service provider, or a local emergency response team, such as the police or fire departments.

While the invention has been specifically described in connection with certain specific embodiments thereof, it may be understood that this is by way of illustration and not of limitation, and the scope of the appended claims should be construed as broadly as the prior art will permit. For example, the order of the steps 204 through 210 may be changed without affecting the invention. 

1. A method for preventing deflagration in a household dryer comprising a cabinet having a drying chamber, comprising: determining the presence of carbon monoxide in the dryer that is indicative of at least one of a fire and a potential for a fire; and initiating a deflagration prevention cycle for the dryer in response to the determination.
 2. The method according to claim 1 wherein determining the presence of carbon monoxide comprises determining the presence of carbon monoxide in the cabinet.
 3. The method according to claim 2 wherein the determining the presence of carbon monoxide comprises sensing the presence of carbon monoxide in the drum.
 4. The method according to claim 2 wherein the sensing comprises monitoring the output signal of a carbon monoxide sensor.
 5. The method according to claim 1 wherein the dryer further comprises a door that provides access to the drying chamber, and wherein the initiating of the deflagration prevention cycle comprises locking the door.
 6. The method according to claim 5 wherein the initiating of the deflagration prevention cycle further comprises terminating operation of a heater in the dryer.
 7. The method according to claim 6 wherein the initiating of the deflagration prevention cycle further comprises terminating operation of a drying fan.
 8. The method according to claim 5 wherein the initiating of the deflagration prevention cycle further comprises terminating operation of the dryer.
 9. The method according to claim 1 wherein the initiating of the deflagration prevention cycle comprises terminating operation of a heater in the dryer.
 10. A method for preventing deflagration in a household dryer comprising a rotatable drum located within a cabinet having a drying chamber accessed by a door, comprising: determining the presence of carbon monoxide in the dryer that is indicative of at least one of a fire and a potential for a fire; and locking the door of the dryer in a closed position.
 11. The method according to claim 10 wherein the determining the presence of carbon monoxide comprises sensing the presence of carbon monoxide in the cabinet.
 12. The method according to claim 11 wherein the sensing the presence of carbon monoxide in the cabinet comprises sensing the presence of carbon monoxide in the drum.
 13. The method according to claim 10 wherein the determining comprises monitoring the output signal of a carbon monoxide sensor.
 14. The method according to claim 13, further comprising terminating operation of a heater in the dryer.
 15. The method according to claim 14, further comprising termination operation of a fan in the dryer.
 16. The method according to claim 15, further comprising terminating operation of the dryer.
 17. The method according to claim 10, further comprising terminating operation of a heater in the dryer.
 18. A household dryer comprising: a cabinet defining an interior and having a drying chamber therein; a door mounted to the cabinet and selectively moveable between an opened and closed position for closing access to the drying chamber; a rotatable drum located within the cabinet; a fire detector located within the cabinet; a door lock coupled with the door and selectively operable between a locked and unlocked position; and a controller operably coupled with the fire detector and the door lock to effect movement of the door lock from the unlocked to the locked position in response to a detection of at least one of a fire and a potential for a fire by the fire detector.
 19. The household dryer according to claim 18 wherein the fire detector comprises a carbon monoxide sensor.
 20. The household dryer according to claim 18 wherein the fire detector comprises a smoke detector.
 21. The household dryer according to claim 20 wherein the smoke detector comprises a photoelectric detector.
 22. The household dryer according to claim 18 wherein the fire detector is located exteriorly of the drum.
 23. The household dryer according to claim 18, further comprising a heating element operably coupled with the controller, wherein the controller terminates power to the heating element in response to a detection of at least one of a fire and a potential for a fire by the fire detector. 